- field1 = f.object || CustomFieldPair.new
- field2 = f.object.respond_to?(:paired_with) ? field1.paired_with : CustomFieldPair.new

%table{class: :pairs}
  = fields_for("pair[0]", field1) do |first|
    = fields_for("pair[1]", field2) do |second|
      %tr
        %td
          .label.top Hint:
          = first.text_field :hint
        %td= spacer
        %td
          .label.top
            %span Required:
            = first.check_box :required
            %br
            %span Disabled:
            = first.check_box :disabled
            = first.hidden_field :id
            = second.hidden_field :id
            %div{style: 'width: 240px;'}
